The response of reinforced concrete members subjected to combined loading which includes torsion is investigated theoretically for a static monotonically increasing load. A unified model, which is an extension of the space truss model, is developed to solve this problem for rectangular, circular and slab sections. A nonlinear beam element which is based on the results from the space truss model is used in the analysis of grid structures on which torsion is known to be significant. By comparison with available experimental data as well as examination of the behavior of the model in extreme conditions, the use of the structural mechanism of the space truss model is verified. The application of the models to some typical torsional problems suggests the conclusion that the existence of torsion may have significant influence on the response of the structure, especially as it relates to the strength of the structure to support the applied load.